A Study Of Distributed Optical Fiber Temperature Sensing System Based On Raman Scattering

The technology of optic fiber sensing was formed gradually with the progress of the produce of optical fiber and the development of optical communication. The research and design of optical fiber sensor have developed greatly since the 70th of the last century. The distributed optic fiber temperature sensing system is designed for the application of a large-scale muti-point measurment of temperature. This system is capable of measuring the distribution of the temperature along the sensing fiber. The distributed optic fiber sensing system has such advantages as immunity to flammability,explosion,high voltage and electromagnetism. Therefore,the study on it arouse the focus all over the world and have made a lot of achievements. The basic theory and technology of the distributed optical fiber sensing system based on spontaneous Raman scattering is discussed and studied in this paper. The present reserch situation of distributed optic fiber sensors are introduced firstly. And Raman scattering theory is analyzed theoretically. Then the general model of the distributed system is put forward. Three measrements schemes are simulating by computer. On the basis of that,A test is designed for observation the intensity of the Anti-Stokes and Stokes modulated by various temperatures. An optimized choice for the incidence laser's central wavelength is simulated mathematically. At the same time,a high power pulsed laser diode with the central wavelength 980nm is checked. Then the technologies of wavelength de-multiplexer and multiplexer are studied and compared. According the peculiarity of the Raman scattering, A new type of wavelength de-multiplexer and multiplexer based muti-cavity thin film filters is designed especially for the utility of Raman scattering sensing. Its actualization is accounted for particularly. With these instructions this new wavelength de-multiplexer and multiplexer is produced and have excellent performance. Lastly, the subsystem of photon dection is described and a circuit with low noise and high gain and broad band is designed. With the corporation of a high speed A/D data sample card, the distributed measurment to the temperature can be realized and nice results are acquired.